Glaucoma

What is Glaucoma?

Glaucoma is an eye disease that gradually steals your vision. Often glaucoma has no symptoms and can suddenly result in vision loss. Without proper treatment, glaucoma can lead to blindness. The good news is that with regular eye exams, early detection, and treatment, you can preserve your sight.


How the eye works


To understand glaucoma you must understand how the eye works. A tough white covering called the sclera protects the eye. Part of the white sclera can be seen in the front of the eye. A clear, delicate membrane called conjunctiva covers the sclera. At the front of the eye is the cornea. The cornea is the clear part of the eyes protective covering. It allows light to enter the eye. The iris is the colored part of your eye that contracts and expands so the pupil can let just the right amount of light into the eye. The light is directed by the pupil to the lens. The lens focuses the light on the retina. Nerve fibers in the retina carry light and images to the brain through the optic nerve.

The front part of the eye is filled with a clear fluid (called intraocular fluid or aqueous humor) made by the ciliary body. The fluid flows out through the pupil. It is then absorbed into the bloodstream through the eye’s drainage system (a meshwork of drainage canals around the outer edge of the iris.) Proper drainage helps keep eye pressure at a normal level. The production flow, and drainage of this fluid is an active, continuous process that is needed for the health of the eye. The inner pressure of the eye (intraocular pressure or IOP) depends on the amount of fluid in the eye. If your eyes drainage system is working properly, then fluid can drain freely out and prevent a buildup. Likewise, if your eye’s fluid system is working properly, then the right amount of fluid can be produced for a healthy eye. Your IOP can vary at different times of the day, but normally stays within a range that the eye can handle.


The Eye with Glaucoma

In most types of glaucoma, the eye’s drainage system becomes clogged so the intraocular fluid cannot drain. As the fluid builds up, it causes pressure to build within the eye. High pressure damages the sensitive optic nerve and results in vision loss.

Symptoms

With open angle glaucoma, the most common form, there are virtually no symptoms. Usually, no pain is associated with increased eye pressure.

Vision loss begins with peripheral or side vision. You may compensate for this unconsciously by turning your head to the side, and may not notice anything until significant vision is lost. The best way to protect your sight from glaucoma is to get tested. If you have glaucoma, treatment can begin immediately.


Different types of Glaucoma

The two main types of glaucoma are primary open angle glaucoma (POAG), and angle closure glaucoma. These are marked by an increase of intraocular pressure (IOP), or pressure inside the eye. When optic nerve damage has occurred despite a normal IOP, this is called normal tension glaucoma. Secondary glaucoma refers to any case in which another disease causes or contributes to increased eye pressure, resulting in optic nerve damage and vision loss.


Open-Angle Glaucoma

This is the most common form of glaucoma, affecting about three million Americans. It happens when the eye’s drainage canals become clogged over time. The inner eye pressure (also called intraocular pressure or IOP) rises because the correct amount of fluid can’t drain out of the eye. With open angle glaucoma, the entrances to the drainage canals are clear and should be working correctly. The clogging problem occurs further inside the drainage canals, similar to a clogged pipe below the drain in a sink.

Most people have no symptoms and no early warning signs. If open angle glaucoma is not diagnosed and treated, it can cause a gradual loss of vision. This type of glaucoma develops slowly and sometimes without noticeable sight loss for many years. It usually responds well to medication, especially if caught early and treated.


Angle Closure Glaucoma

This type of glaucoma is also known as acute glaucoma or narrow angle glaucoma. It is much more rare and is very different from open angle glaucoma in that the eye pressure usually rises very quickly.

This happens when the drainage canals get blocked or covered over, like a sink with something covering the drain.

With angle closure glaucoma, the iris is not as wide and open as it should be. The outer edge of the iris bunches up over the drainage canals, when the pupil enlarges too much or too quickly. This can happen when entering a dark room.

A simple test can be used to see if your angle is normal and wide or abnormal and narrow. Treatment of angle closure glaucoma usually involves surgery to remove a small portion of the outer edge of the iris. This helps unblock the drainage canals so that the extra fluid can drain. Usually surgery is successful and long lasting. However, you should still receive regular check-ups.

Symptoms of angle closure glaucoma may include headaches, eye pain, nausea, rainbows around lights at night, and very blurred vision.


Normal Tension Glaucoma (NTG)

Normal tension glaucoma is also known as low-tension glaucoma or normal pressure glaucoma. In this type of glaucoma, the optic nerve is damaged even though intraocular pressure (IOP) is not very high. Doctors do not know why some people’s optic nerves suffer damage even though pressure levels are in the “normal” range (between 12-22 mm Hg).

Those at higher risk for this form of glaucoma are people with a family history of normal tension glaucoma, people of Japanese ancestry, and people with a history of systemic heart disease, such as irregular heart rhythm. Normal tension glaucoma is usually detected after an examination of the optic nerve.

The Glaucoma Research Foundation sponsored a collaborative international study to help determine the best treatment for this type of glaucoma. The study concluded that eye drops used to lower intraocular pressure were effective even in cases of normal tension glaucoma. Currently, most doctors treat normal tension glaucoma by keeping normal eye pressures as low as possible with medicines, laser surgery, or filtering surgery.


Pediatric Glaucoma

The pediatric glaucomas consist of congenital glaucoma (present at birth), infantile glaucoma (appears during the first three years), juvenile glaucoma (age three through the teenage or young adult years), and all the secondary glaucomas occurring in the pediatric age group.

Congenital glaucoma is present at birth and most cases are diagnosed during the first year of life. Sometimes symptoms are not recognized until later in infancy or early childhood.

The range of treatment is very different from that for adult glaucoma. It is very important to catch pediatric glaucoma early in order to prevent blindness.


Secondary Glaucoma

Glaucoma can occur as the result of an eye injury, inflammation, tumor or in advanced cases of cataract or diabetes. It can also be caused by certain drugs such as steroids. This form of glaucoma may be mild or severe. The type of treatment will depend on whether it is open angle or angle closure glaucoma.


Pseudoexfoliative Glaucoma

This form of secondary open angle glaucoma occurs when a flaky, dandruff-like material peels off the outer layer of the lens within the eye. The material collects in the angle between the cornea and iris and can clog the drainage system of the eye, causing eye pressure to rise.

Pseudoexfoliative Glaucoma is common in those of Scandinavian descent. Treatment usually includes medications or surgery.


Pigmentary Glaucoma

A form of secondary open angle glaucoma, this occurs when the pigment granules in the back of the iris (the colored part of the eye) break into the clear fluid produced inside the eye. These tiny pigment granules flow toward the drainage canals in the eye and slowly clog them, causing eye pressure to rise. Treatment usually includes medications or surgery.


Traumatic Glaucoma

Injury to the eye may cause secondary open angle glaucoma. This type of glaucoma can occur immediately after the injury or years later.

It can be caused by blunt injuries that “bruise” the eye (called blunt trauma) or by injuries that penetrate the eye.

In addition, conditions such as severe nearsightedness, previous injury, infection, or prior surgery may make the eye more vulnerable to a serious eye injury.


Irido Corneal Endothelial Syndrome (ICE)

This rare form of glaucoma usually appears in only one eye, rather than both. Cells on the back surface of the cornea spread over the eye’s drainage tissue and across the surface of the iris, increasing eye pressure and damaging the optic nerve. These corneal cells also form adhesions that bind the iris to the cornea, further blocking the drainage channels.

Irido Corneal Endothelial Syndrome occurs more frequently in light-skinned females. Symptoms can include hazy vision upon awakening and the appearance of halos around lights. Treatment can include medications and filtering surgery. Laser therapy is not effective in these cases.

Treatment

A variety of options are available to treat glaucoma. These include eye drops, laser procedures, and surgery. All are intended to decrease eye pressure and, thereby, protect the optic nerve.

Eye drops used in managing glaucoma decrease eye pressure by helping the eye’s fluid to drain better and/or decreasing the amount of fluid made by the eye.

Laser

For patients who cannot tolerate medications or for whom medication alone has not been adequate, laser treatment continues to be an excellent alternative. It should be noted that laser may also be used as primary treatment. The advantage of this approach is that if adequate pressure lowering is achieved with laser treatment alone, the need for taking a daily medication may be delayed, along with the associated side effects. The effect of laser treatment is typically not permanent, and many patients will eventually require medications. The most common laser treatments for glaucoma are argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT). A new type of laser treatment called MicroPulse laser trabeculoplasy (MLT) is currently being studied as yet another option for effectively increasing drainage of eye fluid to lower pressure

Information on this page is adapted from http://www.glaucoma.org -- the website of the Glaucoma Research Foundation in San Francisco, California -- and is copyrighted by the Glaucoma Research Foundation."

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